v8.0.18

[rel-v8r0]

*Core

FIX: (#6923) cast method names to string before sending monitoring
FIX: (#6905) TornadoREST - fix errors in the exposed methods resolution

*Resources

FIX: (#6920) HTCondorCEComputingElement - set _CONDOR_AUTH_SSL_CLIENT_CADIR before executing condor commands
FIX: (#6909) better handle exceptions in AREXCE

*FrameworkSystem

FIX: (#6919) stdoutJson logger prints all the necessary fields
FIX: (#6919) MicrosecondJsonFormatter does not dump DIRAC specific fields (timeStampIsShown, colorIsShown, etc)

*WorkloadManagementSystem

FIX: (#6918) make singletons of VirtualMachineDB and PilotAgentsDB
FIX: (#6909) config helper error message
FIX: (#6906) SiteDirector: failure in submitting Accounting or Monitoring report only prints an error